La-doped SrTiO_3 films with large cryogenic thermoelectric power factors

摘要

The thermoelectric properties at temperatures between 10 K and 300 K of La-doped SrTiO_3 thin films grown by hybrid molecular beam epitaxy (MBE) on undoped SrTiO_3 substrates are reported. Below 50 K, the Seebeck coefficients exhibit very large magnitudes due to the influence of phonon drag. Combined with high carrier mobilities, exceeding 50000 cm~2 V~(-1) s~(-1) at 2K for the films with the lowest carrier densities, this leads to thermoelectric power factors as high as 470μWcm~(-1)K~(-2). The results are compared with other promising low temperature thermoelectric materials and discussed in the context of coupling with phonons in the undoped substrate.